1. Field of the Invention
The present invention relates to an optical waveguide apparatus that includes an optical waveguide sheet and an optical device. In this specification, an optical waveguide sheet or optical sheet is a waveguide which permits light transmission form a light transmitting unit toward a direction different from a direction oriented from the light transmitting unit to a light receiving unit, as well as light transmission form the light transmitting unit to the light receiving unit, for example.
2. Description of the Related Background Art
In recent years, performances of portable apparatuses, such as personal computers, cellular phones and personal digital assistants (PDAs), and digital audio-visual apparatuses have been increasingly improved, and their interconnections are being developed using all kinds of frequency bands in both of wireless and wire forms. Therefore, appropriate prompt measures are needed to cope with malfunctions of digital equipment due to electromagnetic interference from electric substrates (electromagnetic interference: EMI), immunity from intervention of external electric waves (immunity), and signal errors resulting from defective connections (signal integrity (SI)). With those electromagnetic-wave problems, products prior to shipment are required to clear regulation magnitudes prescribed in the electric-wave regulation law, and development costs for taking those measures continuously increase. In this situation, the optical wiring without any electromagnetic induction is expected to radically solve the above bottleneck.
Further, in the near future the high-speed interconnect environment will be surely established also in homes, so that there is a need to prevent the malfunction and noise intervention even when high-speed electronic equipment is freely connected in a variety of ground environments. Also in this respect, the optical interconnection is an effective means that can readily achieve an electric isolation from the ground.
Various methods of the optical wiring interconnection have been proposed. FIG. 1 illustrates an optical wiring structure 1100 disclosed in Japanese Patent Application Laid-Open No. 9(1997)-270751. In FIG. 1, reference numeral 1120 designates an electric circuit board. Reference numeral 1130 designates an emitting end of optical signals S1, S2 and S3. Reference numeral 1133 designates an optical-signal input portion. Reference numeral 1101 designates an optical bus. Reference numeral 1134 designates an optical-signal output portion. Reference numeral 1140 designates a receiving end of optical signals S1, S2 and S3. Optical devices 1132 and 1142 driven by driver circuits 1131 and 1141 are mounted at the output and input ports 1130 and 1140, respectively. The optical device 1132 is optically coupled to the waveguide sheet 1101 through a 45-degree mirror (optical-path converting unit) 1133s. 
In the structure of FIG. 1, the positioning or alignment between the optical device 1132 and the optical bus (waveguide sheet) 1101, more specifically, between the optical device 1132 and the mirror 1133s, is critically important when light from the optical device 1132 is to be coupled to the optical bus 1101.
It is an object of the present invention to provide an optical waveguide apparatus that facilitates the alignment between an optical device and an optical path converting unit, an optical device, and an opto-electric mixture wiring substrate.
According to one aspect of the present invention, there is provided an optical waveguide apparatus that includes an optical waveguide sheet, and an optical device integrated with an optical-path converting unit. The optical sheet can include a guide unit for setting the optical device therein.
According to another aspect of the present invention, there is provided an optical waveguide apparatus that includes an optical waveguide sheet, an optical device, and a guide unit for setting the optical device therein, which is formed on the optical sheet or a layer on the optical sheet. An optical-path converting unit can be provided at a place in the optical sheet immediately below the guide unit.
According to another aspect of the present invention, there is provided an optical device that is a surface optical device integrated with an optical-path converting unit, which is to be mounted on an optical waveguide sheet. The surface optical device is a surface optical device in a broad sense which includes an end emitting semiconductor laser connected to a 45-degree mirror that can emit light perpendicularly to a substrate, as well as a vertical cavity surface emitting laser (VCSEL) and a surface photodiode. The optical-path converting unit changes a propagation direction of light emitted from the optical device from a direction perpendicular to the optical sheet to a direction parallel to the optical sheet, or changes a propagation direction of light directed to the optical device from a direction parallel to the optical sheet to a direction perpendicular to the optical sheet.
The above optical device is integrated with the optical-path converting unit, such as a conical mirror, a semispherical mirror, and a prism. The prism has a reflective and refractive surface, while the mirror has a reflective surface. With such an optical device, no special means needs to be formed in the optical waveguide sheet on which the optical device is to be mounted. The optical device with the optical-path converting unit can be set at a desired location of the optical sheet at which a guide hole or the like is formed, so that the optical device can be positioned at a location corresponding to an appropriate electrode pad formed on the electric circuit board.
Therefore, the above optical device is more advantageous than the case where a mirror or the like is formed in the optical waveguide sheet in the following point. There is no need to align the optical device with the mirror when the optical device is mounted on the optical sheet, and no special processing of the optical sheet is needed. Thus, an optical waveguide apparatus for the optical wiring can be achieved with excellent productivity.
When a two-dimensional slab waveguide is used as the optical sheet, the conical mirror enables signal transmission and receiving to be performed in all directions parallel to the slab waveguide. When the 45-degree mirror is also used, signal transmission and receiving along a desired direction can be executed together with the signal transmission and receiving in all directions. Where one two dimensional slab waveguide is used, signal multiplexing will be basically performed using the time division sharing, i.e., parallel-serial conversion. However, when a line waveguide (a linear waveguide) is formed in the two-dimensional slab waveguide, parallel transmission with independent channels can be employed for necessary lines as well.
More specifically, the following specific constructions are possible. The optical device can be mounted on a mounting substrate, and the optical-path converting unit can be formed of a polymer. Alternatively, the optical device can be in a bare-chip form, and the optical-path converting unit can be formed of a polymer.
The optical-path converting unit can be a device that coverts the optical path by its reflecting action. In this case, the optical-path converting unit can include a conical reflective surface an apex of which is directed toward the center of a functional portion of the optical device, such as a surface emitting device, such that light from the optical device can be reflected in all directions around the apex and distributed over 360 degrees about the apex. The optical-path converting unit also can include a conical reflective surface an apex of which is directed toward the center of a functional portion of the optical device, such as a surface light-receiving device, such that light travelling from all directions around the apex can be reflected toward the optical device and received thereby. Further, the optical-path converting unit can include a semispherical reflective surface that has substantially the same function as that of the conical reflective surface, or can include a multi-sided pyramid reflective surface that has about the same function as that of the conical reflective surface. Furthermore, the optical path converting unit can include a 45 degree mirror that reflects light from the optical device toward a predetermined direction in the optical sheet, or that reflects light from a predetermined direction in the optical sheet toward the optical device to be received thereby. In addition, the optical-path converting unit can principally receive signal light from a predetermined direction, or principally transmit signal light toward a predetermined direction.
The optical-path converting unit also can be an element, such as a prism and a half-mirror, that achieves the optical-path conversion by its function of reflection and refraction. In this case, the optical path converting unit can include a conical reflective and refractive surface an apex of which is directed toward a direction opposite to the center of a functional portion of the optical device, such as a surface emitting device, such that light from the optical device can be reflected and refracted in all directions around the apex and distributed over 360 degrees about the apex. The optical-path converting unit also can include a conical reflective and refractive surface an apex of which is directed toward a direction opposite to the center of a functional portion of the optical device, such as a surface light-receiving device, such that light travelling from all directions around the apex in the optical sheet can be reflected and refracted toward the optical device and received thereby.
Where the optical device is a surface emitting device, the device can be a surface light emitting diode (LED), or a vertical cavity surface emitting laser (VCSEL), for example. Where the optical device is a surface light-receiving device, the device can be a surface photodiode, for example.
Typically, both opposite electrodes of the optical device are drawn out on a side of the substrate surface of the optical device opposite to a side on which the optical-path converting unit is integrated. Thereby, the optical device can be readily set at a location of the optical sheet corresponding to appropriate electrode pads on the electric circuit board.
According to yet another aspect of the present invention, there is provided an optical waveguide apparatus that includes an optical waveguide sheet of a two-dimensional slab waveguide, and the above-discussed optical device integrated with an optical-path converting unit. The optical device is mounted on the optical sheet by embedding the optical-path converting unit in the optical sheet. The optical device is optically coupled to the optical sheet through the optical-path converting unit such that light transmission and receiving of an optical signal can be achieved in the optical sheet.
The above apparatus is more advantageous than a case where a mirror or the like is formed in the optical waveguide sheet in the following point. There is no need to align the optical device with the mirror when the optical device is set on the optical sheet, and no special processing is needed in the optical sheet. Thus, an optical waveguide apparatus for the optical wiring can be achieved with excellent productivity.
Further, since the two-dimensional slab waveguide is used as the optical sheet, signal transmission and receiving can be performed in all directions parallel to the slab waveguide when the conical mirror or the like is used as the optical-path converting unit of the optical device. When the optical device with the 45-degree mirror is used together with the optical device with the conical mirror or the like, signal transmission and receiving along a desired direction can be performed as well as the signal transmission and receiving in all directions. Where one two-dimensional slab waveguide is used, signal multiplexing will be basically performed using the time division sharing, i.e., parallel-serial conversion. However, when the line waveguide is formed in the two-dimensional slab waveguide, or a plurality of two dimensional slab waveguides are layered, parallel transmission with independent channels can also be employed for necessary lines.
When electric wires are further formed on the optical sheet and the optical sheet has a bendable flexible structure, a portion of the electric wiring in an electric board with large scale integration (LSI) and the like mounted thereon can be replaced by the optical wiring of the optical waveguide apparatus of the present invention. Accordingly, the problem of EMI can be solved at relatively low costs without any extensive design alteration.
According to yet another aspect of the present invention, there is provided a two-dimensional optical waveguide sheet which is to be used in the above optical waveguide apparatus and which includes a line waveguide for performing optical transmission and receiving along a predetermined channel independent of other optical transmission and receiving, or a two-dimensional optical waveguide sheet which is to be used in the above optical waveguide apparatus and which includes a metal pattern for the electric wiring formed thereon.
According to yet another aspect of the present invention, there is provided an opto-electric mixture wiring substrate in which the above optical device integrated with the optical-path converting unit is mounted on and electrically connected to an electric circuit board such that the electric wiring in the electric circuit can be at least partly replaced by the optical wiring of the optical waveguide apparatus to operate an electronic apparatus thereby. Accordingly, a portion of the wiring in an electric board with LSI and the like mounted thereon can be executed by the optical waveguide apparatus of the present invention, and an opto electric mixture wiring substrate can be hence constructed. Thereby, the problem of EMI can be solved at relatively low costs without any extensive design alteration of the electric board.
In the above opto-electric mixture wiring substrate, the optical device can be set on an LSI package of the electric circuit board. Further, the optical waveguide apparatus can be flexible such that it can be approximately tightly mounted on an uneven surface of the electric circuit substrate with passive components and LSI mounted thereon.
According to yet another aspect of the present invention, there is provided a method of fabricating the optical device of the present invention in which the outer profile of the optical path converting unit is formed by heating a flatly shaped polymer to a temperature near its glass-transition temperature and pressing an appropriately-shaped mold against the heated polymer.
More specifically, a transparent polymer or the like is put on a surface of the surface light-emitting or light-receiving device, and the polymer is shaped into the above-discussed mirror configuration. Where individual devices are separated by dicing after those structures are collectively formed in a two dimensional array on a wafer, the optical devices with the optical path converting unit can be mass-produced.
According to yet another aspect of the present invention, there is provided a method of fabricating the optical waveguide apparatus of the present invention in which the outer profile of each optical path converting unit is differently formed according its purpose, a hole corresponding to the outer profile of the optical path converting unit integrated with a desired optical device is formed, and each optical device is self-selectively set in the optical waveguide sheet, or a method of fabricating the optical waveguide apparatus of the present invention in which the optical waveguide sheet is heated to a temperature near its glass-transition temperature, and the optical device integrated with the optical-path converting unit is pushed into a desired location of the heated optical sheet and mounted thereat. When the optical device is self-selectively mounted as discussed above, efficiency of the fabrication process can be raised.
According to yet another aspect of the present invention, there is provided an optical waveguide apparatus that includes an optical waveguide sheet for transmission and receiving of an optical signal, in which there is arranged a guide unit for guiding and fixing an optical device or an electric device in a desired manner such that an electric circuit or an opto-electric circuit can be built on the optical sheet. In the optical waveguide apparatus, an alignment process of the optical device can be omitted since there is arranged a guide hole for mounting the optical device such that it can be optically coupled to the optical sheet through the optical-path converting unit such as a semispherical mirror, a 45 degree mirror, a prism, and a grating, for example. An electric wiring for driving the optical device can be formed in the guide hole. An electrode for driving the device can be formed by bonding the optical device to the electric wiring with a conductive adhesive such that the electric contact can be secured. Accordingly, no special component or means for alignment is needed, and an optical mounting structure for the optical wiring, which is advantageous in mass-productivity, can be achieved.
The following specific configurations are also possible. The guide unit can be a guide hole that enables the optical device to be mounted at a position at which the optical device can couple to the optical waveguide sheet.
There can be further arranged in the optical waveguide sheet an optical-path converting unit for inputting or outputting light along a direction forming a predetermined angle (for example, perpendicularly) relative to the plane of the optical sheet, such that the optical device set in the guide unit can be optically coupled to the optical sheet through this optical path converting unit. More specifically, a protrusion of the optical path converting unit is formed on a substrate or a cladding layer, and a transparent resin of a waveguide core layer is formed on the substrate or cladding layer by dipping, casting, spin coating, or the like. And, another cladding layer is formed on the core layer, and the guide hole for mounting the device is formed by photography and etching, molding, laser-beam processing, or the like. Further, the electric wiring for flip-chip mounting can be formed.
In the above specific structure, the optical path converting unit is used to optically couple the optical device to the optical waveguide sheet. Alternatively, the optical device can be fixed in a predetermined attitude, for example, a slant position, or can be located within the optical waveguide sheet. In these cases, the optical device can be coupled to the optical sheet without any optical-path converting unit.
Where the optical path converting unit is the protrusion formed on the cladding layer, light emitted by the light emitting device fixed in the guide unit can be propagated in the optical sheet through a portion of the core layer formed by transferring of the above protrusion, or light propagating along the core layer can be caused to enter the light receiving device fixed in the guide unit through this portion of the core layer. The optical-path converting unit can also be a portion of the core layer formed by transferring of a protruded portion provided on a mold for forming the core layer.
The optical path converting unit can include a conical or semispherical mirror an apex of which is directed toward the center of a functional portion of the optical device set in the guide unit, such that light from the optical device can be reflected in all directions around the apex and distributed over 360 degrees about the apex. Thereby, light travelling from all directions around the apex along the optical waveguide sheet can be reflected toward the optical device and received thereby. Thus, using the above optical path converting unit, light from the light emitting device fixed in the guide unit can be broadcast in the optical sheet, or light from all light transmission sources in the optical sheet can be received by the light receiving device fixed in the guide unit.
The optical-path converting unit can also include a 45-degree mirror that reflects light from the optical device fixed in the guide unit toward a predetermined direction, or that reflects light from a predetermined direction toward the optical device fixed in the guide unit to be received thereby. Thus, using the above optical-path converting unit, light from the light emitting device fixed in the guide unit can be transmitted toward a predetermined region in the optical sheet, or light from a predetermined light transmission source in the optical sheet can be received by the light receiving device fixed in the guide unit.
Further, line waveguide for performing light transmission and receiving along a predetermined channel between optical devices fixed in the guide units can be formed in the two-dimensional slab waveguide. Where one two dimensional slab waveguide is used, signal multiplexing will be basically performed using the time division sharing, i.e., parallel serial conversion. However, when the line waveguide is formed in the two-dimensional slab waveguide, parallel transmission with independent channels can be employed for necessary lines.
The guide unit can be a guide hole for fixing an electric device, such as a resistor, a capacitor, and an integrated circuit (IC), such that the electric circuit can be built on the optical waveguide sheet. Thus, the optical waveguide apparatus can be versatilely employed.
A metal pattern for driving the optical device, or forming the electric circuit can also be formed on the optical waveguide sheet. In this structure, the terminal of the metal pattern can extend into the guide unit, and when the optical device or the electric device is set in the guide unit, its electrode or terminal is electrically connected to the terminal of the metal pattern.
The guide unit can be a guide hole formed correspondingly to the outer profile of the optical device or the electric device which is to be mounted on the optical sheet, or a guide hole with an inner wall formed correspondingly to the outer profile of the optical device or the electric device and an outer wall of any configuration.
According to yet another aspect of the present invention, there is provided an opto-electric mixture wiring substrate in which the above optical waveguide apparatus is mounted on and electrically connected to an electric circuit board such that the electric wiring of the electric circuit can be at least partly replaced by the optical wiring of the optical waveguide apparatus to operate an electronic apparatus thereby.
In the above opto-electric mixture wiring substrate, the optical waveguide apparatus can be mounted on an LSI package of the electric circuit board. Further, the optical waveguide apparatus can be flexible such that it can be approximately tightly mounted on an uneven surface of the electric circuit substrate with passive components and LSI mounted thereon. When the electric wiring is provided on a bendable and flexible optical waveguide sheet, a portion of the wiring in the electric board with LSI and the like mounted thereon can be executed by the optical waveguide apparatus of the present invention to construct the opto-electric mixture wiring substrate thereby. The problem of EMI can be solved at relatively low costs without any extensive design alteration of the electric board.
Further, a plurality of the optical waveguide apparatuses can be layered, and an electric via penetrating through a portion or all of the stacked optical waveguide apparatuses can be formed such that the electric wiring for driving optical devices on the optical waveguide apparatuses can be connected to the electric circuit board. Thus, the optical waveguide apparatuses need only to be integrated with the electric circuit board when a plurality of signal wirings are to be simultaneously executed. Here, the electric wiring for driving the optical device can be constructed when the optical device and the optical path converting unit are mounted on the optical waveguide sheet and the via filled with a conductor is formed in the stacked optical waveguide sheets. Thus, a multi-layer opto-electric mixture wiring board can be achieved at relatively low costs.
According to yet another aspect of the present invention, there is provided a method of fabricating an optical waveguide apparatus which includes a step of forming an optical-path converting unit in a cladding layer of the optical waveguide, a step of depositing a resin on the cladding layer to form a core layer, a step of depositing another resin on the core layer to form another cladding layer, a step of forming a guide unit for mounting the optical device therein at a predetermined location relative to the optical-path converting unit on the another cladding layer, and a step of forming an electric wiring on the another cladding layer. Alternatively, there is provided a method of fabricating an optical waveguide apparatus which includes a step of depositing a resin on a substrate with a mold for forming an optical path converting unit to form a core layer, a step of forming a guide unit for mounting the optical device therein at a predetermined location relative to the optical-path converting unit on the core layer, a step of forming an electric wiring on the core layer, and a step of removing the core layer from the substrate.
Those fabrication methods can further include a step of flip-chip bonding the optical device on the guide unit such that the optical device can be brought into an electric contact with the electric wiring.
These advantages, as well as others will be more readily understood in connection with the following detailed description of the preferred embodiments and examples of the invention in connection with the drawings.